1. Field of the Invention
The invention relates to a stirring element, especially a gasing stirring element for stirring of liquids to which a gas, for example, air, is supplied, with a hub for attachment to a stirring shaft, and a support disk joined to the hub; a plurality of stirring blades is attached to the peripheral edge of the support disk.
2. Description of Related Art
A gas supplied to a liquid to be stirred is dispersed into bubbles as small as possible by means of a gasing stirring element in order to form a large surface for mass transfer between the gas and liquid.
Usually this gasing stirring element comprises a disk stirrer with stirring blades and an annular gas distributor, along whose apex line round holes are formed which holes feed the gas to the rotating disk stirrer, by whose shearing action the gas is further dispersed. The rotational motion of the stirring element, however, produces a negative pressure on the back of the stirring blades which leads to formation of gas cushions there. These gas cushions impart a streamlined contour to the stirring blades which is expressed in a strong power drop at given rpm.
Since, for mass transfer, two parameters, specifically the amount of gas and the power input, are determined by the stirring process, in order to be able to control the adjustment of the desired mass transfer, the power reduction deficit must be balanced by increasing the rpm. This engenders considerable cost in control engineering and hardware.